When children face difficult experiences like neglect or abuse, their bodies and brains can undergo significant stress.
This stress can disrupt brain development, which may contribute to mental health challenges such as depression and schizophrenia. Until recently, scientists were unsure of the specific processes behind this connection.
In a recent study, researchers at KAIST (Korea Advanced Institute of Science and Technology) led by Professor Won-Suk Chung made a major breakthrough in understanding how childhood stress impacts the brain.
They discovered that when children are under high levels of stress, a type of brain cell called astrocytes can become overactive and start removing essential connections between nerve cells.
This process, known as “synaptic pruning,” is normal during brain development but becomes harmful when it removes too many connections due to stress.
Astrocytes usually support brain health by getting rid of unneeded or damaged parts of nerve cells.
However, under prolonged stress, these cells can go beyond their normal role, disrupting important pathways that the brain relies on for healthy functioning. This disruption can increase the risk of mental health issues.
Stress prompts the body to release hormones, which help us manage short-term challenges by reducing inflammation and aiding energy use.
But in situations of ongoing stress, especially from traumatic experiences in childhood, the body produces high levels of stress hormones over a long period.
This continuous hormone production can harm the brain, potentially leading to issues with mood, thinking, and social interactions.
The researchers at KAIST found that stress hormones attach to a part of the astrocytes called glucocorticoid receptors. This triggers the astrocytes to produce an enzyme known as Mer tyrosine kinase, which intensifies the removal of brain connections.
To explore this, the researchers studied young lab mice that had been socially isolated, which caused them significant stress. They found that these stressed mice had more active astrocytes that were excessively pruning brain connections.
Surprisingly, this process only affected certain types of connections in the brain. The selective removal of these connections led to unusual patterns between nerve cells, which affected the mice’s social abilities and caused signs of depression as they aged.
The researchers noted that another brain cell type, called microglia, did not exhibit the same response to stress, suggesting that astrocytes have a unique role in stress-related brain changes.
To understand if this might also happen in humans, the team conducted tests on human brain cells grown in the lab. They observed similar behavior: when exposed to stress hormones, human astrocytes also removed an excessive number of connections.
This finding supports the idea that astrocytes may play a role in mental health problems in people who experienced high stress levels in childhood.
Professor Chung explained that until now, scientists had not fully understood how early-life stress could lead to brain disorders. This research suggests that astrocytes removing too many nerve cell connections may be a key part of the process.
He hopes that, in the future, treatments for stress-related brain conditions might focus on controlling astrocytes’ responses to stress.
The findings were published in the scientific journal Immunity, providing new insights that could lead to better ways to address mental health issues linked to childhood stress.
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